Timing the millisecond pulsars in 47 Tucanae   总被引：1，自引：0，他引：1  

P.C. Freire  F. Camilo  D.R. Lorimer  A.G. Lyne  R.N. Manchester  N. D'Amico 《Monthly notices of the Royal Astronomical Society》2001,326(3):901-915

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The fraction of galaxies that contain active nuclei and their accretion rates     

M.J. Page 《Monthly notices of the Royal Astronomical Society》2001,328(3):925-930

We investigate the relationship between the present-day optical luminosity function of galaxies and the X-ray luminosity function of Seyfert 1s to determine the fraction of galaxies that host Seyfert 1 nuclei and their Eddington ratios. The local type 1 active galactic nuclei (AGN) X-ray luminosity function is well reproduced if ∼1 per cent of all galaxies are type 1 Seyferts which have Eddington ratios of ∼10⁻³. However, in such a model the X-ray luminosity function is completely dominated by AGN in E and S0 galaxies, contrary to the observed mix of Seyfert host galaxies. To obtain a plausible mix of AGN host galaxy morphologies requires that the most massive black holes in E and S0 galaxies accrete with lower Eddington ratios, or have a lower incidence of Seyfert activity, than the central black holes of later-type galaxies.  相似文献   

Luminous and dark matter in the Milky Way     

Rob P. Olling  Michael R. Merrifield 《Monthly notices of the Royal Astronomical Society》2001,326(1):164-180

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Spectral index determination between 408 MHz and 5 GHz in the northern sky     

A.W. Jones  R.J. Davis  A. Wilkinson  G. Giardino  S.J. Melhuish  H. Asareh  R.D. Davies  A.N. Lasenby 《Monthly notices of the Royal Astronomical Society》2001,327(2):545-551

We present the joint analysis of two 5-GHz interferometric surveys of the northern sky, taken with different baselines. The two surveys were carried out on the Jodrell Bank 5-GHz interferometer based at Manchester. The Maximum Entropy Method is used to check the consistency of the two surveys and the final two-dimensional maps are used, together with low-frequency full sky surveys, to put constraints on the Galactic spectral index. It is found that synchrotron emission is the dominant process at high Galactic latitudes below 5 GHz.  相似文献   

The magnetic field and wind confinement of β Cephei: new clues for interpreting the Be phenomenon?     

J.-F. Donati  G.A. Wade  J. Babel  H_f. Henrichs  J.A. de Jong  T.J. Harries 《Monthly notices of the Royal Astronomical Society》2001,326(4):1265-1278

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Propagation of disturbances in the solar chromosphere and corona (II)     

Bo Li  Hui-nan Zheng  Shui Wang 《Chinese Astronomy and Astrophysics》2002,26(4):456-468

The first part of this article presents an analytic discussion of the linear properties of magnetohydrodynamic (MHD) wave propagation. Then, with a 2-dimensional, time-dependent, compressible MHD simulation subject to a self-consistent non-isothermal, non-uniform initial state, we study numerically the global propagation process following an initial pressure pulse applied at the base of the chromosphere. Our numerical results indicate that, if the pulse is applied near the pole, there are two modes, one fast, one slow of magnetoacoustic waves; whereas if the pressure pulse is applied near the equator, there is a fast mode and a standing disturbance located near the source. These results may help interpret the wave events observed by SOHO/EIT.  相似文献   

Observations of high co rotational lines in post-AGBs and PN     

K. Justtanont  A. G. G. M. Tielens  C. J. Skinner  M. R. Haas 《Astrophysics and Space Science》1995,224(1-2):305-308

We present a preliminary interpretation of high CO rotational line data obtained from KAO. The possibility of either a PDR or a shock model is considered in order to explain the observations.  相似文献   

A flare in the mira X oph     

S. Etoka  A. M. Le Squeren 《Astrophysics and Space Science》1995,224(1-2):455-456

Before the observation of the 1974 U Ori eruption, it was considered that the Mira stars had only some regular OH variations. With this eruption, we realized that sometimes flares can occur in this type of star. In the course of an OH Mira star monitoring programme with the Nançay radio telescope, we have discovered a new eruptive type of OH maser emission in several sources. Especially, in early 1992, we observed a quickly rising 1665 Mhz emission in the Mira X Oph. The main characteristics of this flare were: large flux variations independent of the light curve; large degree of circular polarization; radial velocity emission close to the stellar velocity.  相似文献   

河外射电源的结合阵数据的图像处理     

张福俊 Akuj.  CE 《天文学报》1995,36(3):245-251

不同类型的射电望远镜阵的分辨率差异甚大，用它们的数据进行图像处理后所得到的源结构的尺度也不一样。为了得到中间尺度的结构信息，有时我们需要把不同类型的射电望远镜阵的观测数据结合起来再进行图像处理。本文阐述我们把不同类型阵的数据结合时所用的方法；也给出我们使用的方法所获得的结果的实际例子。  相似文献   

Statistical Properties of the Highest Pulses in Gamma-Ray Bursts   总被引：1，自引：0，他引：1  

Yi-Ping Qin  En-Wei Liang  Guang-Zhong Xie  Cheng-Yue SuNational Astronomical Observatories  Yunnan Observatory  Chinese Academy of Sciences  Kunming  qinyp@public.km.yn.cnDepartment of Physics  Guangxi University  Nanning  eloy@iaa.esDepartment of Physics  Guangdong Industry University  Guangzhou 《中国天文和天体物理学报》2003,3(1):38-48

We study the statistical properties of the highest pulses within individual gamma-ray bursts (GRBs). A wavelet package analysis technique and a developed pulse-finding algorithm have been applied to identify the highest pulses from burst profiles observed by BATSE on board CGRO from 1991 April 21 to 1999 January 26. The statistical light curves of the highest pulses in four energy channels have been derived by an aligning method, which illustrate the temporal evolution of the pulse emission. Our result that narrower pulses go with higher energies is consistent with previous findings. By normalizing both the pulse durations and counts to unity, “characteristic” profiles of the highest pulses in the four channels are also derived. The four characteristic profiles are turned out to be almost the same, thus strongly support the previous conclusion that the temporal profiles in different energy channels are self-similar and the previous conjecture on GRB pulses, implying that the emission process is similar at different energies. The cosmological time dilation effect is examined by investigating the relationship between the pulse flux and pulse duration. An anti-correlation between the two was found, which agrees with the expectation of the cosmological time dilation effect. Also, the evolution of the pulse duration with the observational epoch is studied. The result shows that the pulse duration tends to be shorter in later epochs. This trend cannot be explained by the present theoretical models, and may represent a great challenge to current theories.  相似文献